10,103 research outputs found
The Transit Light Curve Project. VI. Three Transits of the Exoplanet TrES-2
Of the nearby transiting exoplanets that are amenable to detailed study,
TrES-2 is both the most massive and has the largest impact parameter. We
present z-band photometry of three transits of TrES-2. We improve upon the
estimates of the planetary, stellar, and orbital parameters, in conjunction
with the spectroscopic analysis of the host star by Sozzetti and co-workers. We
find the planetary radius to be 1.222 +/- 0.038 R_Jup and the stellar radius to
be 1.003 +/- 0.027 R_Sun. The quoted uncertainties include the systematic error
due to the uncertainty in the stellar mass (0.980 +/- 0.062 M_Sun). The timings
of the transits have an accuracy of 25s and are consistent with a uniform
period, thus providing a baseline for future observations with the NASA Kepler
satellite, whose field of view will include TrES-2.Comment: 15 pages, including 2 figures, accepted Ap
The Transit Light Curve Project. VIII. Six Occultations of the Exoplanet TrES-3
We present photometry of the exoplanet host star TrES-3 spanning six
occultations (secondary eclipses) of its giant planet. No flux decrements were
detected, leading to 99%-confidence upper limits on the planet-to-star flux
ratio of 0.00024, 0.0005, and 0.00086 in the i, z, and R bands respectively.
The corresponding upper limits on the planet's geometric albedo are 0.30, 0.62,
and 1.07. The upper limit in the i band rules out the presence of highly
reflective clouds, and is only a factor of 2-3 above the predicted level of
thermal radiation from the planet.Comment: To appear in AJ [14 pages
Spitzer Infrared Observations and Independent Validation of the Transiting Super-Earth CoRoT-7b
The detection and characterization of the first transiting super-Earth,
CoRoT-7 b, has required an unprecedented effort in terms of telescope time and
analysis. Although the star does display a radial velocity signal at the period
of the planet, this has been difficult to disentangle from the intrinsic
stellar variability, and pinning down the velocity amplitude has been very
challenging. As a result, the precise value of the mass of the planet - and
even the extent to which it can be considered to be confirmed - have been
debated in the recent literature, with six mass measurements published so far
based on the same spectroscopic observations, ranging from about 2 to 8 Earth
masses. Here we report on an independent validation of the planet discovery,
using one of the fundamental properties of a transit signal: its achromaticity.
We observed four transits of CoRoT-7 b with Spitzer, in order to determine
whether the depth of the transit signal in the near-infrared is consistent with
that observed in the CoRoT bandpass, as expected for a planet. We detected the
transit and found an average depth of 0.426 {\pm} 0.115 mmag at 4.5 {\mu}m,
which is in good agreement with the depth of 0.350 {\pm} 0.011 mmag found by
CoRoT. These observations place important constraints on the kinds of
astrophysical false positives that could mimic the signal. Combining this with
additional constraints reported earlier, we performed an exhaustive exploration
of possible blends scenarios for CoRoT-7 b using the BLENDER technique. We are
able to rule out the vast majority of false positives, and the remaining ones
are found to be much less likely than a true transiting planet. We thus
validate CoRoT-7 b as a bona-fide planet with a very high degree of confidence,
independently of any radial-velocity information. Our Spitzer observations have
additionally allowed us to significantly improve the ephemeris of the planet.Comment: Accepted by Ap
Absolute properties of the low-mass eclipsing binary CM Draconis
Spectroscopic and eclipsing binary systems offer the best means for
determining accurate physical properties of stars, including their masses and
radii. The data available for low-mass stars have yielded firm evidence that
stellar structure models predict smaller radii and higher effective
temperatures than observed, but the number of systems with detailed analyses is
still small. In this paper we present a complete reanalysis of one of such
eclipsing systems, CM Dra, composed of two dM4.5 stars. New and existing light
curves as well as a radial velocity curve are modeled to measure the physical
properties of both components. The masses and radii determined for the
components of CM Dra are M1=0.2310+/-0.0009 Msun, M2=0.2141+/-0.0010 Msun,
R1=0.2534+/-0.0019 Rsun, and R2=0.2396+/-0.0015 Rsun. With relative
uncertainties well below the 1% level, these values constitute the most
accurate properties to date for fully convective stars. This makes CM Dra a
valuable benchmark for testing theoretical models. In comparing our
measurements with theory, we confirm the discrepancies reported previously for
other low-mass eclipsing binaries. These discrepancies seem likely to be due to
the effects of magnetic activity. We find that the orbit of this system is
slightly eccentric, and we have made use of eclipse timings spanning three
decades to infer the apsidal motion and other related properties.Comment: 19 pages, 9 figures. Accepted for publication in Ap
Caso edificio Space
The Space building was a residential complex located in the city of MedellÃn (Colombia), which was divided into six stages or towers. In the last stage of the project, tower six suffered a structural failure that caused its collapse, which led to the demolition of the other towers. The main issues discussed are related to the design of structures, columns, beams, and loads that a structure can withstand given the terrain and the materials used for construction. In addition, the study carried out by the Universidad de Los Andes, which was the main source of information in the investigation of the collapse and its aftermath, will be presented. This article will collect and show information on this case in the areas directly related to civil engineering and what happened to those involved in the project.El edificio Space fue un conjunto residencial ubicado en la ciudad de MedellÃn (Colombia), el cual se dividÃa en seis etapas o torres. En la última etapa del proyecto, la torres seis, sufrió una falla estructural que produjo el colapso de esta, y esto llevó a la demolición de las demás torres. Los problemas principales que se trataron están relacionados con el diseño de estructuras, columnas, vigas y cargas que puede soportar una estructura dadas las situaciones del terreno y los materiales utilizados para la construcción. Además, se dará a conocer el estudio realizado por la Universidad de Los Andes la cual fue la principal fuente de información en la investigación del colapso y posteriormente a este. El presente artÃculo recolectará y mostrará información de este caso en los ámbitos ligados directamente a la ingenierÃa civil y lo ocurrido con los implicados en el proyecto
Effectiveness of different disinfection techniques of the root canal in the elimination of a multi-species biofilm
The purpose of the study was to evaluate the effectiveness of different root canal disinfection techniques in the elimination of a multi-species biofilm from inside the root canal. Fifty mandibular first premolars were used in the present study, standardized to 11mm of root length, and instrumented with a reciprocation system Reciproc, (VDW GmbH, Munich, Germany) to a #50. Longitudinally sectioned halves of the roots were obtained and washed with NaOCl 4%, EDTA 17% and 5% sodium thiosulfate, and sterilized by autoclaving for 15 minutes at 121°C. A multi-species biofilm broth was developed with three strains of bacteria under laboratory conditions: Enterococcus faecalis ATTC 29212, Eikenella corrodens ATTC 23834, Streptococcus anginosus ATTC 33397. Roots were autoclaved and transferred to the broth for 4 days and then were subjected to either disinfection with sodium hypochlorite 4% and XP-endo Finisher (FKG Dentaire, La Chaux-de-Fonds, Switzerland) or chlorhexidine 2% with and without activation with XP-endo Finisher (FKG Dentaire, La Chaux-de-Fonds, Switzerland). The evaluations of the biofilm elimination showed results that indicate that the 4% sodium hypochlorite group with positive pressure irrigation presented significant differences with the group that had irrigation with sodium hypochlorite activated with XP-endo Finisher and the chlorhexidine groups to 2% (P<0.05). Chlorhexidine 2% activated with the XP-endo Finisher does not exert elimination or improved cleaning effect on the multi-species biofilm. Activation of sodium hypochlorite 4% improved the elimination of the multi-species biofilm
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